Sheet sizing issues

[darth-cheney]

There are currently a couple of issues with Sheet and sheet table cell sizing.

First, a sheet is not limited by the bounds of its parent, and is often extending (overflowing) in either direction. You can see this currently in all cells demo examples.

Second, individual td elements are adding a mysterious right margin that is not accounted for in styling, but only when:

1. There is large text that has been "ellipsed" and overflow cutoff, and:
2. There is not a selection happening

Oddly, when a selection happens, the td cells seem to "collapse" down to the correct size.

[darth-cheney]

The two issues here have preliminarily been fixed in commits 2077347 and e523c95 respectively